Segmented stator

ABSTRACT

In the segmented stator assembly disclosed, four teeth extend inwardly, and rectangularly relative to each other, from surrounding segments. The teeth form a bore at the center of the assembled segments. Each tooth has two parallel edges one of which extends along a line passing through the center of the bore. The centerline of each tooth is offset from the bore center. Coil-carrying bobbins are mounted on respective teeth so their axes coincide with the centerlines of the teeth on which they are mounted. The offset of each bobbin leaves space for intrusion of an edge of the transversely directed adjacent bobbin.

United States Patent Kasargod et al. 1 51 Feb. 22, 1972 [s41 SEGMENTEDSTATOR 2,145,791 1/1939 Gille ..3l0/2l8 m1 Swim-1d M Sim-11w 313%???3/132? 2311;: .jiiliiisi Shankar Abhyankar, both of 0/0 Elec- 485,220l1/l892 Pepper..... 1,353,658 9/1920 KOStko ..3l0/258 6 1 I 5 o PPrimary Examiner-William M. Shoop, Jr. Assistant Examiner-R. SkudyAttorney-McGlew & Toren ABSTRACT In the segmented stator assemblydisclosed, four teeth extend inwardly, and reetangularly relative toeach other. from surrounding segments. The teeth form a bore at thecenter of the assembled segments. Each tooth has two parallel edges oneof which extends along a line passing through the center of the bore.The centerline of each tooth is offset from the bore center.Coilcarrying bobbins are mounted on respective teeth so their axescoincide with the centerlines of the teeth on which they are mounted.The offset of each bobbin leaves space for intrusion of an edge of thetransversely directed adjacent bobbin.

7 Claims, 5 Drawing Figures PATENTEDFEB22 I972 3,644, 767

SHEET 2 UF 2 Invenlor sntonum vnnsnm smewwns $.93 Wm y if/(win wt.-

Attorney This invention relates to a segmented stator adapted for use.

in electromechanical devices such as fractional horsepower inductionmotors, induction-type relays, rotary solenoids or differentialtransformer type position sensors.

As known in the art, an important problem that arose in the constructionof such stators, for example in fractional horsepower motors was thedifficulty -of winding stators having relatively small bores. Because ofthe small bore size, it was found difficult to manually insert the coilsin the stator slots. In order to obviate this difficulty, the stator nowcomprises a plurality of stator segments. Segmented stators are known inthe art, which comprise a plurality ofsegments and wherein a bobbin orformer having a coil wound thereon is held onto the tooth of eachsegment. One particularly known construction consists of a stator havingeight such segments, each of said segments having a tooth holding abobbin carrying the coil. In such a construction, the center line ofeach of the tooth passes through the center of the bore circle. Oneadvantage of such a construction, namely of a stator having eightsegments, is that it allows an easy winding of the coils on the stator.However, an essential disadvantage of such a known construction of asegmented stator is that is was necessary to provide a fourpole windingfor the stator, as opposed to a two-pole winding which would be moreefficient for a given radial airgap between the stator and the rotor. Afurther disadvantage of such a known construction is that the coils werenot of a uniform rectangular cross section. This would be apparent sincethe slots formed between the teeth of adjacent segments of aneight-piece segmented stator could not provide the required slot shapefor the introduction of coils with uniform rectangular cross section.Another disadvantage associated with such a known construction is withregard to the introduction of the bobbins or formers on the teeth. Sinceeach tooth was widened at its top with the dual objective of loweringthe magnetic reluctance of associated airgap and securely confining thecoils to the slots between the teeth, a complete bobbin having aprewound coil thereon could not, as such, be introduced onto a tooth.For this purpose, it was necessary to assemble the bobbin, in separateparts, on a tooth ofa segment,

and thereafter finally wind the coil on the bobbin held to the tooth ofsaid segment.

An object of this invention is to propose a construction of segmentedstator suitable for use in electromechanical devices and which avoidsthe disadvantages associated with the prior art.

A further object of this invention is to propose a segmented statorwherein the said stator is assembled from four segments only, whereby itis enabled to receive a two-pole winding.

Yet another object of this invention is to propose a segmented statorwherein a coil is prewound on a bobbin or former prior to introductiononto the tooth ofa segment forming said stator.

SUMMARY OF THE INVENTION According to this invention there is provided asegmented stator, suitable for use in electromechanical devices such asfractional horsepower induction motors, induction-type relays, rotarysolenoids or differential transformer type position-sensors, consistingof four individual segments assembled together to form said stator, eachof said segments having a tooth depending therefrom and adapted todirectly receive a bobbin or former, the centerline of said tooth beingoffset from the center of the bore circle.

Further objects and advantages of this invention will become apparentfrom the ensuing description when read in conjunction with theaccompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a plan view of theassembled stator without the stator windings;

FIG. 2 shows one of the four segments incorporated in said stator;

FIG. 3 shows a bobbin carrying a winding; FIG. 4 shows a stator segmentonto which a prewound bobbin has been introduced;

FIG. 5 shows the assembled stator together with the bottom carryingwindings.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings, and inparticular to FIG. 2, there is shown a stator segment 1 consisting ofanumber of laminations 2 stacked and riveted together at point 3. Theadvantages of such a laminated structure are already known in the art.

An assembly of four such segments 1 constitutes the complete stator 4 asshown in FIG. 1. The joint between adjacent segments 1, as shown in FIG.1, is constructed by the plane surfaces 5 in contact and therebyresulting in a single plane contact. However, in order to reduce themagnetic reluctance between adjacent segments, it is also possible toprovide atongue-and-groove joint giving enhanced contact between theadjacent segments 1 (not shown).

As will be apparent from FIG. 1, the center line A of each tooth 6 isoffset from the center B of the stator bore circle. The provision of atooth 6 with such an offset center line A forms one of the importantaspects of this invention in that by such a provision, the followingadvantages accrue;

1. It is possibleto secure a higher tooth inner area and a lower airgapmagnetic reluctance, without having to widen the tooth 6 at the top;

2. As no widening of the tooth 6 is required at its top, a coil 7 may beprewound on a bobbin 8, and the bobbin 8 carrying the coil subsequentlyslipped over the tooth 6 on each segment 1.

3. When the segments 1 are assembled, the coil 7 on each segment ispreferably confined to the slot space 9 by adjacent segment;

4. Coils of a uniform rectangular cross section can be used,

without sacrificing slot space.

Another important aspect of the present invention is that only foursegments are used in the assembly of the stator 4, as opposed to eightsegments used in the stators known in the prior art. The use of onlyfour segments not only facilitates manufacture but also enables atwo-pole winding for the stator 4 as opposed to four-pole winding whichonly is possible on stators with eight segments. A two-pole windingpermits the use of larger airgaps between the stator and rotor in orderto achieve a given efficiency, as compared to a motor with fourpolewinding. The advantage of a larger airgap is that it makes themanufacture of such motors easier.

Reference is now made to FIG. 3 which illustrates a bobbin or former S,carrying a winding or coil 7 whose ends are brought out to the twoterminals 10. In accordance with this invention, the coils are prewoundon a former or bobbin 8, suitably impregnated in a known manner, andthereafter slipped on to the tooth 6 of a segment 1 as shown in FIG. 4.Thus, whereas in the prior known construction, such a bobbin 8 having aprewound coil 7 thereon, could not be slipped onto the tooth 6 of asegment 1 such a procedure is now possible with the segments 1 of thepresent invention. Further, since the coils 7 have a uniform rectangularcross section and can be prewound onto a bobbin 8 prior to itsintroduction in the segments 1, multiple coil winding with standardcoil-winding machines intended for that purpose, becomes readilypossible.

Referring now to FIG. 5, a complete stator assembly 11 comprising fourof said segments 1, each of the said segments 1 carrying a bobbin 8 withprewound coil 7, held together within a cylindrical outer shell 12 isshown. However, the segments 1 can also be assembled without the shell12 by making use of the motor and shields (not shown) to hold thesegments together. The coils 7 on the individual segments 1 areinterconnected in a manner appropriate to the electric supply, whethersingle phase, two phase or three phase, from which the motor is tooperate.

We claim:

l. A segmented stator assembly, comprising four individual segmentsassembled together to form a stator, each of said segments having atooth extending inwardly of the stator for receiving a bobbin, a totalnumber of teeth in said stator being four, the length of said teethbeing rectangularly oriented relative to each other, said teeth forminga center bore, the centerline of each of said teeth being offset fromthe center of the bore, each ofsaid teeth having a longer side and ashorter side, radial lines extending from the center of said boreparallel to the centerlines of said teeth being closer to said shortersides of said teeth than to the centerline thereof.

2. An assembly as in claim 1, wherein each of said teeth includesparallel edges and forms an inner end and a body, the inner end having awidth in a range whose maximum is equal to the width of the body so asto allow direct axial insertion of the bobbin.

3. A stator assembly as in claim 1, wherein a bobbin is mounted on eachof said teeth, each of said bobbins including respective coils woundthereon.

4. A stator assembly as in claim 3, wherein said coils wound on thebobbin have uniform rectangular sections.

5. A stator assembly as in claim 1, wherein the centerlines of each ofsaid teeth is offset so that radial lines extending parallel to each ofthe centerlines intersects the tooth having a centerline to which theradial line is parallel.

6. A stator assembly as in claim 5, wherein a bobbin is mounted on eachof said teeth, each of said bobbins including

1. A segmented stator assembly, comprising four individual segmentsassembled together to form a stator, each of said segments having atooth extending inwardly of the stator for receiving a bobbin, a totalnumber of teeth in said stator being four, the length of said teethbeing rectangularly oriented relative to each other, said teeth forminga center bore, the centerline of each of said teeth being offset fromthe center of the bore, each of said teeth having a longer side and ashorter side, radial lines extending from the center of said boreparallel to the centerlines of said teeth being closer to said shortersides of said teeth than to the centerline thereof.
 2. An assembly as inclaim 1, wherein each of said teeth includes parallel edges and forms aninner end and a body, the inner end having a width in a range whosemaximum is equal to the width of the body so as to allow direct axialinsertion of the bobbin.
 3. A stator assembly as in claim 1, wherein abobbin is mounted on each of said teeth, each of said bobbins includingrespective coils wound thereon.
 4. A stator assembly as in claim 3,wherein said coils wound on the bobbin have uniform rectangularsections.
 5. A stator assembly as in claim 1, wherein the centerlines ofeach of said teeth is offset so that radial lines extending parallel toeach of the centerlines intersects the tooth having a centerline towhich the radial line is parallel.
 6. A stator assembly as in claim 5,wherein a bobbin is mounted on each of said teeth, each of said bobbinsincluding respective coils wound thereon.
 7. A stator assembly as inclaim 1, wherein the centerline of each of said teeth is offset from thecenter of the bore such that radial lines extending from the bore centerto the points of intersection of the inner face and the shorter of thetwo sides of each of said teeth, are substantially parallel to thecenterlines of the teeth to which the radial lines are drawn.